The present disclosure generally relates to brake valves. More particularly, the present disclosure relates to an improved, multi-function, air valve for use in connection with spring applied air release parking brakes typically used in heavy-duty truck trailers.
It is known in the truck-trailer art to employ parking brakes of the type where large spring brakes are normally apply a braking force, and an accompanying air chamber is pressurized to counteract the springs and release the force. Thus, if there is a loss in pressurized air in the system, the pressure in the brake chamber is consequently reduced and the spring brakes applied.
Likewise, these vehicles often incorporate a pressure protection valve in the system to protect the tractor's air supply and prevent automatic apply of trailer spring brakes with a supply system failure.
Still another type of valve often used in truck-trailers is an anti-compounding valve intended to limit the application of additional pressure to the service brakes when the spring brakes are already applied. U.S. Pat. No. 5,284,384 discloses an arrangement that combines these different valves into a single housing. The multi-function spring brake valve with anti-compounding, pressure protection and quick release functions are performed by multiple valve clusters. However, the prior art arrangement uses a shuttle loaded valve for pressure protection and a single biased check valve for anti-compounding, as well as routing the air through the valve chambers in a very specific manner.
Moreover, the prior art valve structures do not provide significant differential, and particularly does not advantageously use hysteresis on a supply curve side. Although the prior art single purpose and multi-function valves perform their respective functions, such valves generally operate in an inefficient manner, and do not teach or show a valve with unique valve clusters or portions to prevent air flow to an on/off parking valve structure, nor a quick-exhaust diaphragm that achieves a special measure of differential.
Accordingly, there is a need for a multi-function valve that provides a valve as a combined unit that includes (i) an on/off parking valve cluster or portion, (ii) a second valve cluster or portion for protecting and filling a trailer reservoir, and (iii) a third valve cluster or portion to prevent compounding of the brakes by preventing fluid communication to the on/off parking valve portion and venting air out the evacuated system passage or port, i.e., a bias double check, as well as a solution to one or more of the deficiencies from which the prior art valves have suffered.